Diaphragm for gramophones, phonographs, telephones, and the like



A. T. COLLIER.

DIAPHRAGM FOR GRAMOPHONES, PHONOGRAPHS, TELEPHONES, AND THE LIKE. APPLICATION FILED SEPL26, 1919.

.1,385,243. Patented July 19, 1921.

MM g y/ 551/245 UNITED STATES PATENT OFFICE.

DIAPHRAGM FOR GRAMOPHONES, PHONOGRAPHS, TEIJEPHONES, AND THE LIKE.

Specification of Letters Patent.

Patented July 19, 1921.

Application filed September 26, 1919. Serial No. 326,622.

To allrwho'm it may concern:

Be it known that I, ARTHUR THOMAS Con- LIER a subject of the Kin of Great Britain, residing at St. Albans, land, have invented new and useful Improvements in Diaphra s for Gramohones Phonographs, Te ephones, and the tike, of which the following is a specificaion.

This invention relates to diaphragms for gramophones, phonographs, telephones, and the like of the kind com rising a fiat apertured part of one materiail and a fiat part of another material covering or closing this aperture.

It has heretofore been proposed to provide a diaphragm with a cupped edge, and a ring movable relatively to the sound box frame and arranged to apply variable tension to the diaphragm.

According to this invention there is provided a dlaphragm comprising an apertured part of one material and a part of another material covering or closing this a rture, in combination with means for app ying variable tension to the compound diaphra This tension is applied to all parts 0 the diaphragm being communicated to the part closing the aperture by the surrounding apertured part.

This compound diaphragm is mounted on the sound box in a manner similar to that employed for mounting the parchments of drums, for example, by clamping the outer edge of the diaphragm on to the frame or casing of the sound box by means of a split ring the ends of which are drawn together by screws, the said outer edge of the diap ragm being cupped for the purpose, or by cementing or otherwise securing this cupped edge of the diaphragm to a ring mounted around or co-axially with the said frame or casing.

To subject the diaphragm to the requisite tension a ring may be (provided to press against the diaphragm a j o the sound box frame or casing, this ring being moved or adjusted by means of set screws, or the rin to which the diaphragm is cemented or ot erwise secured as above mentioned may itself be similarly adjustable relatively to the sound box frame or casing.

In the accompanying drawing I have shown how the said invention may be conertfordshire, Engacent to the edgeveniently and advantageously carried into practice. In this drawing:

Figure 1 is a front View and Fig. 2 a central section of a diaphragm constructed according to this invention, mounted on a sound box casing.

Fig. 3 is a front view of a diaphragm mounted on a sound box casing, illustrating a modified construction of diaphragm.

Figs. 4 and 5 are views similar to Fig. 2; illustrating modifications of the method of stretching or obtaining the requisite tension in the diaphragm.

As shown in Fi 1 and 2 a is a diaphragm part of a p acid or supple sheet material which becomes sonorous when subjected to tension and which has a relatively low natural period of vibration, such as archment, vellum, or thin celluloid, havmg an aperture therein which is covered or closed by a diaphragm part b of mica, glass, natural ivory, or other more brittle or ri material than that of the art a and having a relatively higher natura period of vibration. The edge of the aperture in the part a is serrated or slit so as to provide tongues c which are alternately cemented to opposite sides of the part b. The two parts of the compound diaphragm are thus brought substantially into one plane. This method of joining the adjacent edges of the parts of the diaphragm can be applied to the construction of diaphragms having more than two parts respectively made of the alternative materials mentioned above, or equivalents thereof.

The outer edge of the part a is cupped so as to fit around the outer cylindrical surface of the sound box frame (Z to which it-is secured without the use of a cement or adhesive, b means of a clamping or split ring 6 provi ed with lugs f and a tlghtening screw 9. The compound iaphragm can then be readil removed and replaced, as desired. In this arrangement the outer cylindrical surface of the said frame (1 and the corresponding inner face of the ring, between which the parchment is clamped, may either of them, or both, be roughened, and if desired a small strip or plate 6 of metal may be inserted at the split part of the ring 6 to prevent puckering of the parchment as the ring is tightened to clamp it around the sound box frame cl.

The lugs f may be formed with extensions h suitably shaped to provide a support for the ivotal mounting of a stylus bar.

hen the above described arrangement of clamping ring 6 is employed a stretching ring i is arranged within the sound box frame in which it is adjustable by means of screws y. This ring 71 has an integral apertured back plate is so that, as the ring 2' is advanced out of the frame d to stretch the diaphragm, the depth of the space immediately behind the diaphragm remains constant. A vulcanite, compressed fiber or like washer may be arranged under the points of the adjusting screws j to prevent jarring.

In Fig. 3 a modified construction of compound diaphragm is illustrated. In this case the mica part b overlaps the parchment part a/ and is secured thereto by a suitable adhesive. The edge of the mica part is covered by a ring m of paper, tracing cloth, parchment or the like, also secured by a suitable adhesive such as fish glue, and instead of plain circular edges as shown these parts may be serrated or of other desired form to avoid a sharp line of demarcation between the different materials.

The cupped edges of the compound diaphragm, instead of being held beneath a clamping ring, may be cemented or otherwise fastened to a ring a as shown in Fig. 4, provided with set screws j by which the ring n is forced away from the sound box frame d in order to subject the diaphragm to tension and hold these parts together. The diaphragm shown in Fig. 4 is similar in construction to that shown in Fig. 3. In the arrangement shown in Fig. 5, the sound box frame 03 is provided with a cylindrical extension a supporting a ring 12 having a conical surface 9 over which the cupped edge of the diaphragm is drawn and fastened. The ring 7 is. adjusted by screws j. If desired, the edge of the frame d (or d) over which the compound diaphragm is drawn may be rounded or beaded or it may be covered or provided with a projecting india rubber or like ring against which the diaphragm is tightly drawn.

In the application of this invention to the diaphragm of a telephone receiver a part of the compound diaphragm is made of ferrotype iron or other suitable magnetic material and in its application to a telephone transmitter the diaphragm comprises a carbon part.

By employing a compound diaphragm under tension as herein described a more exact recording and reproduction of sounds is obtained than when using a diaphragm of a single material since overtones or other components of the sounds to which one material is unresponsive will be recorded and reproduced by a part of the diaphragm of another material.

I claim 1. A sound recording or reproducing diaphragm comprising a flat apertured outer part of a supple material which is sonorous when stretched, and a flat inner part of a more rigid material closin the aperture in the first-mentioned part and having its outer margin firmly connected to the margin around the said aperture.

2. A sound recording or reproducing diaphragm comprising a flat apertured outer part of a supple material which is sonorous when stretched, a flat inner part of a more rigid material closing the aperture in the first-mentioned part, and a layer of adhesive material connecting a marginal portion of the inner part to a marginal portion around the aperture in the outer part.

3. A sound recording or reproducing diaphragm comprising a fiat apertured outer part of one material, a fiat inner part of another material closing the aperture in the first-mentioned part, a distinct ring of material covering the joint between the said inner and outer parts on one side of the diaphragm and a layer of adhesive material securing the said ring to the said outer and inner parts.

ARTHUR THOMAS COLLIER.

Witnesses:

GEORGE HARRISON, CONRAD ARNOLD. 

